1. Field of the Invention
The invention relates to a backlighting device, more particularly to a backlighting device capable of providing uniform brightness.
2. Description of the Related Art
The display panels used in mobile phones, PDAs, digital cameras, and the like normally operate in conjunction with a backlighting source. Generally, light is radiated from a plurality of point light sources, such as light emitting diodes, is incident on a light guide plate, and is then reflected from the light guide plate to the display panel. Referring to FIG. 1, the light emitted from the light emitting diodes 11 is seldom uniformly incident on the light guide plate 12. In other words, the light from the light emitting diodes 11 is incident on the light guide plate 12 in a manner that the illuminance is decreased gradually away from a location of the light guide plate 12 where the light is incident along a direction transverse to the light incident direction. Relatively bright areas 13 and relatively dark areas 14 are hence formed on the light guide plate 12, which will in turn form gray areas on the display panel. Therefore, the aforesaid light guide plate 12 is modified in the art by treating the light guide panel 12 with dotting or sand-blasting to form microstructures 15, which are distributed in a manner of varying density, depth or size. However, in order to obtain an optimum effect for a specific light guide plate 12, it is required to perform a series of tests before producing the light guide plate 12. Therefore, it is not easy to mass-produce the light guide plate 12. Furthermore, the light guide plate 12 having a uniform brightness effect can hardly be obtained in the aforesaid method.